The present invention relates to a multimedia information data multiplex transmission system for putting information data of a plurality of kinds each having an arbitrary information content into a single packet and conducting multiplexed radio transmission, and its multiplexer and demultiplexer. The present invention further relates to an error correction encoder and decoder suitable for application to this system.
For implementing radio multimedia, it is necessary to multiplex and transmit media information such as image data, voice data, additional data, and the like. Especially for giving and taking these kinds of information by using a mobile communication terminal, it is important that the information is made to be capable of being transmitted in a poor environment such as a multi-path fading environment.
Heretofore, ITU-T recommendation H.223 has been standardized as a scheme concerning multimedia multiplexing. This scheme implements multimedia multiplexing of packet multiplexing type in an existing telephone network. An example of H.223 is shown in FIG. 13A. In FIG. 13A, LCN represents logical channel, AL adaptation layer, PM packet marker, MUX and multiplexing.
Typically, in a MUX packet, a header is disposed at its head. In succession, four voice bytes (LCN1), one data byte (LCN2), two image (video) bytes (LCN3), one data byte (LCN2), and two image bytes (LCN3) are disposed in the cited order. In the example of FIG. 13A, however, image data finishes in the middle of a MUX packet, and consequently only one byte is accommodated in a two-byte capacity in the last LCN3. This is indicated by setting a PM bit in the next packet header to xe2x80x9c1xe2x80x9d.
The format of the header is shown in FIG. 13B. With reference to FIG. 13B, by referring to an entry of a multiplex table in a four-bit MC (multiplex code) field, it is specified which media information is represented by each byte of an information field. A three-bit HEC (header error control) field provides an error detection function of the MC field using a three-bit CRC. (As for details, see xe2x80x9cITU-T Draft recommendation H.223, for example.)
By the way, H.223 has been determined on condition that multimedia multiplexing of packet multiplexing type is implemented in an existing telephone network having a comparatively fine transmission quality as described above. In order to raise the transmission efficiency, the header is protected by the three-bit CRC alone.
In radio multimedia communication, however, the transmission channel state is made poor by fading or the like. If it is attempted to apply H.223 to radio multimedia communication as it is, therefore, then such a situation cannot be coped with by the CRC of three bits or so, and header errors frequently occur. This results in a problem that contents of the multiplex table cannot be read and discard of MUX packets frequently occurs.
Furthermore, the length of the MUX packets is not always constant, but changes according to the information content of each media information as shown in the example of FIG. 13A as well. If packets of such a variable length are transmitted through a poor radio transmission channel, then packet synchronizing cannot be attained or the packet length cannot be found on the receiving side, resulting in frequent discard of MUX packets.
On the other hand, payloads containing information such as data, voice, and data cannot be decoded correctly either regardless of the received result of header information, if the radio transmission channel is brought into a poor state. Heretofore, therefore, there has been proposed such a scheme as to protect the payload by applying convolution encoding to information of each of image, voice, and data. (As for details, see, for example, xe2x80x9cProposal for High Level Approach of H.324/Annex C Mode 1xe2x80x9d, Q11-A-11b, ITU-T Q11/WP2/SG16, June 1997.)
If it is attempted to securely protect the information of the payload, however, it is necessary to encode all of the information to be protected, resulting in a lowered transmission efficiency. This is a serious problem especially in a system having a limited transmission band such as a mobile communication system.
As a scheme for putting information data of a plurality of kinds such as multimedia information into a packet and conducting multiplex transmission, there is a scheme standardized on condition that transmission is conducted via a wire telephone network as heretofore described. If this standardized scheme is employed as it is in a radio communication system, however, detection errors of header information are frequently caused on the receiving side by the poor transmission channel state. Since the multiplex table cannot be read, discard of packets frequently occur. Especially in the case where the packet length is variable, there occurs such a state that the packet synchronizing cannot be attained or the packet length cannot be recognized, resulting in a substantially disabled state in communication.
On the other hand, for the payload, there has. been proposed such a scheme as to protect it by using an error correction code such as a convolutional code. If it is attempted to decode information securely on the receiving side by using a conventional scheme, however, the transmission efficiency of the information significantly falls. This poses an especially serious problem in a mobile communication system in which it is difficult to secure a wide transmission band.
A first object of the present invention is to provide an information data multiplex transmission system and its multiplexer and demultiplexer capable of reproducing header information favorably even in the case where transmission is conducted via a poor transmission channel, thereby reading the multiplex table accurately, and lowering the packet discard rate.
A second object of the present invention is to provide an information multiplex transmission system, its multiplexer and demultiplexer, an error correction encoder, and an error correction decoder capable of decoding and reproducing payloads securely without significantly deteriorating the transmission efficiency even in the case where transmission is conducted via a poor transmission channel, and thereby having a high transmission efficiency and excellent protection performance.
In order to achieve the above described first and second objects, the present invention provides the following configurations.
(1) In an information transmission system for inserting information into a packet and transmitting the packet, a transmitting side generates a plurality of error correction data making the information independently restorable, inserts these error correction data into a packet together with the information in a predetermined position relation, and transmits the packet.
If on the receiving side at least one of a plurality of error correction data can be received and reproduced, it becomes possible owing to such a configuration to correct transmission errors of information on the basis of the error correction data and reproduce the information. For example, even in a mobile communication system having a poor transmission channel quality, therefore, highly reliable information transmission can be conducted.
(2) In an information data multiplex transmission system for inserting a plurality of kinds of information data into one packet and conducting multiplex transmission, a transmitting side generates a plurality of header information pieces, each of the plurality of header information pieces including a multiplex code indicating disposition positions in the packet according to kinds of information data inserted in the packet and including error detection bits for detecting a receiving error of the multiplex code, causes each header information piece to include error correction data making the header information piece independently restorable, inserts header information pieces in predetermined positions of the packet, inserts the plurality of kinds of information data in positions of the packet indicated by the multiplex code, and transmits the packet.
In such a configuration, header are provided with an error correction capability. Even in a mobile communication system having a poor transmission channel quality, therefore, headers can be reproduced correctly. In addition, a plurality of headers are transmitted. If at least one of a plurality of headers can be received and reproduced, therefore, it becomes possible to correct transmission errors of information on the basis of the header and reproduce the information. As a result, packets discarded due to an unreadable multiplex table can be reduced. Even in a mobile communication system or the like having a poor transmission channel quality, therefore, highly reliable information transmission can be conducted.
(3) In the configuration of (2), multiplexing is effected while conducting processing so as to make all packets have a predetermined length. In other words, the packet length is made to be a fixed length. Owing to such a configuration, configuration of the encoding and decoding means can be simplified.
(4) In the configuration of (2), a receiving side extracts one out of a plurality of header information pieces inserted in a packet, conducts error detection and error correction, and, if error correction is impossible, extracts another header information piece and conducts error detection and error correction, and repetitively executes processing of extracting another header information piece and conducting error detection and error correction for all header information pieces until errorless header information piece is reproduced.
By doing so, an errorless header information piece out of a plurality of header information pieces can be reproduced.
(5) If all header information pieces cannot be corrected in error in the configuration of (4), all header information pieces are subjected together to error correction processing using a coupled code.
Even if all header information pieces cannot be individually reproduced, such a configuration makes it possible to reproduce the header information by conducting error correction on all header information pieces collectively.
(6) In an information data multiplexing apparatus of a transmitting apparatus used in an information data multiplex transmission system for inserting a plurality of kinds of information data into one packet and conducting multiplex transmission,
the information data multiplexing apparatus includes: an information content estimation means for estimating information amounts respectively of the plurality of kinds of information data; a multiplex code generation means for generating a first multiplex code indicating disposition positions in the packet on the basis of the information amounts of respective information data estimated by the information content estimation means, and further generating a second multiplex code having a fixed relation with the first multiplex code; a header information generation means for adding error detection and correction code data for detecting and correcting receiving errors to each of the first and second multiplex codes generated by the multiplex code generation means and thereby generating first and second header information; and a packet generation means for storing the information data to be transmitted in the packet together with the first and second header information on the basis of the multiplex codes.
The apparatus of the transmitting side has such a configuration. Even if in the apparatus of the receiving side the first multiplex code cannot be reproduced by itself, therefore, it becomes possible to reproduce the first multiplex code on the basis of the second multiplex code. On the basis of the reproduced multiplex code, each information data can be taken out from the packet.
(7) In the configuration of (6), a parity of the first multiplex code is used as the second multiplex code. In other words, a concatenated code with respect to the first multiplex code is used as the second multiplex code.
(8) and (9) As a concrete example of the concatenated code, a convolutional code and a Hamming code can be mentioned. If a convolutional code is used, the most likelihood decoding scheme can be used. As a result, the error correction capability can be raised. If a Hamming code is used, decoding means complying with H.223 already has an error detection function using the Hamming code, and hence existing decoding means complying with H.223 advantageously need only to be provided with an error correction function.
(10) and (11) As the configuration of the packet generation means, such a configuration as to store the first and second header information in an identical packet, and such a configuration as to store the first and second header information in different packets are conceivable. The former one has an advantage that the insertion and reproduction of header information can be simplified. The latter one has an advantage that the error correction capability against burst errors can be kept high by making time distance between the header information pieces long and thereby providing an interleaving effect.
(12) In the configuration of (6), it is desirable that the multiplex code generation means determines the multiplex codes so as to make all packets have a predetermined length. By doing so, fixed-length packets can be transmitted. In a mobile communication system, highly reliable packet transmission can be effected.
(13) In an information data demultiplexing apparatus of a receiving apparatus used in an information data multiplex transmission system for inserting a plurality of kinds of information data having arbitrary information amounts into one packet and conducting multiplex transmission,
it is now assumed that first and second header information pieces having a multiplex code indicating disposition positions in the packet according to the plurality of kinds of information data and error detection and correction code data for detecting and correcting receiving errors of the multiplex code are stored in the packet, and the plurality of information data are stored in positions of the packet indicated by the multiplex code.
At this time, an information data demultiplexing apparatus of a receiving apparatus includes a header information extraction means for selectively extracting the first and second information pieces from the packet, and first, second, and third demultiplexing means.
First, the first demultiplexing means conducts error detection on the first header information piece. If there are no errors, the first demultiplexing means demultiplexes and outputs the plurality of information data from the packet on the basis of the multiplex code included in the header information piece. When an error is detected by the first demultiplexing means, a second demultiplexing means conducts error correction of the first header information piece and then conducts error detection again. If there are no errors, the second demultiplexing means demultiplexes and outputs the plurality of information data from the packet on the basis of the multiplex code included in the header information piece corrected in error. Furthermore, when an error is detected by the second demultiplexing means as well, the third demultiplexing means conducts error detection of the second header information piece. If there are no errors, the third demultiplexing means demultiplexes and outputs the plurality of information data from the packet on the basis of the multiplex code included in the header information piece.
According to the error occurrence state, the first, second and third demultiplexing means are thus used by stages in order to demultiplex the information data. For example, in such a state that the transmission channel quality is poor, therefore, all of the first to third demultiplexing means are used, and the error detection and error correction of three stages are conducted, accurate information data demultiplexing being made possible. On the other hand, in such a state that the transmission quality is comparatively fine, demultiplexing of the information data can be conducted in a short time.
(14) In the configuration of (13), a fourth demultiplexing means is provided. When an error is detected by the third demultiplexing means, the fourth demultiplexing means conducts error correction of the second header information piece and then conducts error detection again. If there are no errors, the fourth demultiplexing means demultiplexes and outputs the plurality of information data from the packet on the basis of the multiplex code included in the header information piece corrected in error.
(15) In the configuration of (14), a fifth demultiplexing means is further provided. When an error is detected by the fourth demultiplexing means, the fifth demultiplexing means conducts error correction of the first header information piece and the second header information piece collectively and then conducts error detection again. If there are no errors, the fifth demultiplexing means demultiplexes and outputs the plurality of information data from the packet on the basis of the multiplex code included in the first or second header information piece corrected in error.
Even in a case where the transmission channel quality is very poor and the first to third demultiplexing means cannot demultiplex the information data, it becomes possible in the configuration heretofore described to restore the header information by using the fourth and fifth demultiplexing means. As a result, accurate demultiplexing of the information data becomes possible.
(16) When in the configuration of (2) the header information piece includes a packet marker representing a continuation state between packets, a multiplex code field specifying kinds of information data inserted in the packet, and a header error control field having an error detection function, the transmitting side includes means for inserting a plurality of the packet markers in the header information piece repetitively. The receiving side includes means for conducting a majority decision on the plurality of packet markers and reproducing one correct packet marker.
Owing to such a configuration, it becomes possible on the receiving side to reproduce a correct packet marker by using such an extremely simple configuration that a plurality of packet markers are inserted. Even under such a condition that the transmission quality is poor, therefore, packets can be recognized correctly and packet discard ratio can be reduced.
(17) In an information data multiplex transmission system for inserting a plurality of kinds of information data having arbitrary information amounts into one packet, inserting header information including at least a multiplex code indicating disposition positions of the plurality of kinds of informations data within the packet into the packet, and conducting multiplex transmission,
the transmitting side includes a means for adding an error correction code formed of a Reed-Solomon code to at least one of the plurality of kinds of information data.
The receiving side includes a means for conducting error correction decoding processing on the plurality of kinds of information data which have been received, on the basis of error correction codes added to the information data and thereby reproducing the plurality of kinds of information data.
(18) An information data transmitting apparatus includes an error detection code addition means for adding an error detection code to first information data to be transmitted and outputting second information data; an error correction encoding means for encoding the second information data output from the error detection code addition means, by using an error correction code formed of a Reed-Solomon code and outputting third information data; and a header addition means for adding a control header having control information representing a transmission form of the information data inserted therein to the third information data output from the error correction. encoding means.
In such a configuration, error correction can be conducted on the information data while taking a symbol as the unit by using an error correction code formed of a Reed-Solomon code. As a result, it becomes possible to effectively protect the information data from burst errors.
(19) In the configuration of (18), the error correction encoding means conducts error correction encoding on the second information data by using a Reed-Solomon code over GF(28).
This configuration is effective in the case where the information data length is a fixed length. Furthermore, by using a Reed-Solomon code over GF(28), error correction encoding and decoding processing taking 8 bits as the unit becomes possible. Therefore, it is also possible to assure the conformity with H.223 which is an existing scheme.
(20) In the configuration of (18), the error correction encoding means conducts error correction encoding on the second information data by using a shortened Reed-Solomon code.
By using a shortened Reed-Solomon code, the present invention can be applied to variable-length information data as well. In other words, in multimedia communication including images, a variable-length encoding scheme is typically adopted as the image encoding scheme. Therefore, the information data length varies from frame to frame. By conducting error correction encoding by using a shortened Reed-Solomon code, however, the length variation of the information data can also be coped with.
(21) In the configuration of (20), the error correction encoding means includes: an encoder main body for conducting error correction encoding processing on the second information data which has been shift-input by using a shortened Reed-Solomon code; and an order reversal means for shift-inputting a plurality of information elements forming the second information data to the encoder main body in descending order of term degree of an information polynomial and causing the information elements to be subjected to error correction encoding processing.
Owing to such a configuration, a shortened Reed-Solomon encoding processing can be implemented while using a general purpose Reed-Solomon encoder as it is.
(22) In the configuration of (20), the error correction encoding means includes an encoder main body for conducting error correction encoding processing on the second information data which has been shift-input by using a Reed-Solomon code; a comparison means for comparing a length of the second information data with a predetermined fixed length; a null code addition means; and a null code deletion means. If the length of the second information data is judged to be shorter than the fixed length by the comparison means, the null code addition means adds a null code sequence having a length corresponding to a difference to the second information data, shift-inputs the second information data having the null code sequence thus added thereto to the encoder main body, and causes the error correction encoding processing. The null code deletion means deletes a null code sequence corresponding to the null code sequence added by the null code addition means from the information data subjected to error correction decoding in the encoder main body, and outputting a shortened third information data.
Owing to such a configuration, error correction encoding using a shortened Reed-Solomon code can be implemented.
(23) In an information data multiplex transmission system for inserting a plurality of kinds of information data into one packet, inserting header information including at least a multiplex code indicating disposition positions of the plurality of kinds of informations data within the packet into the packet, and conducting multiplex transmission, the transmitting side includes a means for adding an error correction code to first information data to be transmitted, then adding an error correction code formed of a shortened Reed-Solomon code over GF(28) to the information data having the error correction code thus added thereto, further adding a control header having control information representing a transmission form of the information data inserted therein to the information data thus output, and transmitting resultant information data.
The receiving side includes a means for conducting error correction decoding processing on the information data which has been received, on the basis of error correction code formed of the shortened Reed-Solomon code over GF(28) added to the information data and thereby reproducing the information data.
(24) An information data transmitting apparatus includes: an error detection code addition means for adding an error detection code to first information data to be transmitted and outputting second information data; an error correction encoding means for encoding the second information data output from the error detection code addition means, by using an error correction code formed of a shortened Reed-Solomon code over GF(28) and outputting third information data; and a header addition means for adding a control header having control information representing a transmission form of the information data inserted therein to the third information data output from the error correction encoding means.
In the configuration of (23) and (24), the information data can be effectively protected from burst errors by using a Reed-Solomon code. In addition, since a shortened Reed-Solomon code is used, the configuration can be applied to variable-length Reed-Solomon code as well. Furthermore, by using a Reed-Solomon code over GF(28), error correction encoding and decoding processing while taking 8 bits as the unit becomes possible. As a result, the conformity with H.223 which is an existing scheme can be ensured.
(25) In a receiving apparatus for communicating with a transmitting apparatus, the transmitting apparatus generating a first parity signal formed of arbitrary elements according to a first encoding rule with respect to a transmitting signal formed of an arbitrary number of elements, generating a second parity signal formed of an arbitrary number of elements according to a second encoding rule with respect to at least a part of the transmitting signal and the first parity signal, and generating and transmitting a transmitting encoded signal by combining the transmitting signal and the first and second parity signals,
the receiving apparatus includes: a means for receiving the transmitting encoded signal and outputting a received encoded signal including the first and second parity signals; a first decoding means for conducting most likelihood decoding on the received encoded signal including the first parity signal; a second decoding means for conducting most likelihood decoding on a received encoded signal including the first parity signal; a second decoding means for conducting most likelihood decoding on a received encoded signal including the second parity signal; and a means for calculating distance values respectively between decoded signals obtained by the first and second decoding means and the received signal, and reproducing the transmitting encoded signal on the basis of the decoded signal corresponding to a shorter distance.
Owing to such a configuration, the received encoded signal including the first parity signal and the received encoded signal including the second parity signal are decoded by using the most likelihood decoding scheme having a high error correction capability. In addition, on the basis of a decoded signal having higher reliability out of the two decoded signals thus obtained, the transmitted encoded signal is reproduced. As a result, highly reliable signal reproduction can be conducted.
(26) In a receiving apparatus for communicating with a transmitting apparatus, the transmitting apparatus generating a first parity signal formed of arbitrary elements according to a first encoding rule with respect to a transmitting signal formed of an arbitrary number of elements, generating a second parity signal formed of an arbitrary number of elements according to a second encoding rule with respect to at least a part of the transmitting signal and the first parity signal, and generating and transmitting a transmitting encoded signal by combining the transmitting signal and the first and second parity signals,
the receiving apparatus includes: a means for receiving the transmitting encoded signal and outputting a received encoded signal including the first and second parity signals; a first amending and decoding means for amending the received encoded signal including the first parity signal on the basis of a first amending signal, then conducting most likelihood decoding on a resultant signal, outputting a decoded signal together with information representing reliability of the decoded signal, and using the reliability information as the first amending signal; a second amending and decoding means for amending the received encoded signal including the second parity signal on the basis of a second amending signal, then conducting most likelihood decoding on a resultant signal, outputting a decoded signal together with information representing reliability of the decoded signal, and using the reliability information as the second amending signal; and a control means for causing the amending and decoding processing to be repetitively conducted by the first amending and decoding means a predetermined number of times and causing the amending and decoding processing to be repetitively conducted by the second amending and decoding means a predetermined number of times, and reproducing the transmitting encoded signal on the basis of the received encoded signal, the first amendment, and the second amendment.
Owing to such a configuration, the received encoded signal including the first parity signal and the received encoded signal including the second parity signal are decoded by using the most likelihood decoding scheme having an input amending function according to the reliability information. As compared with the case where the most likelihood decoding is simply conducted, further highly reliable signal reproduction can be implemented.
(27) In an information data multiplex transmission system for inserting a plurality of kinds of information data having arbitrary information amounts into one packet and conducting multiplex transmission,
the transmitting side includes: a first encoding means for generating a first parity signal formed of arbitrary elements according to a first encoding rule with respect to a first transmitting signal formed of an arbitrary number of elements; a first interleaving means for altering order of elements of the first transmitting signal; a second encoding means for generating a second parity signal formed of arbitrary elements according to a second encoding rule with respect to a second transmitting signal altered in element order by the first interleaving means; and a means for generating and transmitting a transmitting encoded signal including the first transmitting signal and the first and second parity signals.
The receiving side includes: a means for receiving the transmitting encoded signal, and outputting a received encoded signal including the first received signal, the first received parity signal, and the second parity signal; a first decoding means for adding an adjustment signal formed of an arbitrary number of elements to the first received signal and the first received parity signal, thereby generating a first decoding input signal, and generating a decoding output signal from the first decoding input signal; a first amending means for amending the adjustment signal on the basis of the first decoding output signal; a second interleaving means for conducting interleaving processing on the first received signal, and outputting a second received signal; a second decoding means for adding the adjustment signal to the second received signal and the second received parity signal, thereby generating a second decoding input signal, and generating a second decoding output signal from the second decoding input signal; a second amending means for amending the adjustment signal on the basis of the second decoding output signal; a control means for causing the generation processing of the first decoding output signal in the first decoding means and amending processing of the adjustment signal in the first amending means, and the generation processing of the second decoding output signal in the second decoding means and amending processing of the adjustment signal in the second amending means to be repetitively executed a predetermined number of times; and a means for setting so as to change the number of times of repetition for specific elements of the first and second received signals.
In such a configuration, a favorable effect can be obtained against burst errors by conducting interleaving, in the same way as the case where a plurality of header information pieces are transmitted at time intervals. In addition, in the case where a plurality of header information pieces are transmitted at time intervals, the effect against burst errors is lowered if the packet length is short. Even if the packet length is short, however, a sufficient effect is obtained by conducting interleaving.
(28) In a multiplexing apparatus of an information data multiplex transmission system for inserting a plurality of kinds of information data into one packet and conducting multiplex transmission,
the multiplexing apparatus includes: a division means for dividing each of the plurality of kinds of information data into an important part and an unimportant part; a first error correction encoding means for conducting error correction encoding on the important part resulting from the division in the division means by using a first error correction code; a header generation means for generating first header information representing a boundary between encoded information data of the important part yielded by the first error correction encoding means and the unimportant data; a second error correction encoding means for conducting error correction encoding on a new information data group including the encoded information data of the important part yielded by the first error correction encoding means, the first header information, and information data of the unimportant part, by using a second error correction code; a multiplexing means for inserting encoded information data groups corresponding to the plurality of kinds of information data, yielded by the second error correction encoding means into predetermined positions of the packet, respectively; and a means for adding second header information representing a multiplexing state to the encoded information data groups multiplexed by the multiplexing means.
Owing to such a configuration, it becomes possible to provide an especially important part of the information data with a double error correction function. As compared with case where all information data are subjected to error correction coding under the same condition, therefore, the information data can be transmitted with a high quality without lowering the transmission efficiency.
(29) In (28), the header generation means has a function of generating an error detection code for conducting error detection on the first header information; and the second error correction encoding means conducts error correction encoding on a new information data group including the encoded information data of the important part yielded by the first error correction encoding means, the first header information and the error detection code thereof, and the information data of the unimportant part, by using the second error correction code.
By doing so, it is possible to provide the first header information representing the code length of the information data encoded by using the first error correction code.
(30) In the configuration of (28), the multiplexing apparatus further includes: an acquisition means for acquiring information representing a quality of a transmission channel; and an encoding control means for supplying the new information group to the multiplexing means without conducting the second error correction encoding if the quality of the transmission channel acquired by the acquisition means is better than a predetermined quality.
Owing to such a configuration, the second error correction encoding processing is omitted in the case where the transmission channel is comparatively fine. As a result, the processing delay caused by the decoding processing can be reduced.
(31) In a demultiplexing apparatus of an information data multiplex transmission system for inserting a plurality of kinds of information data into one packet and conducting multiplex transmission,
the demultiplexing apparatus includes: a demultiplexing means for demultiplexing a plurality of kinds of encoded information data groups inserted in a received packet, on the basis of second header information representing a multiplex state thereof; a second error correction decoding means for conducting second error correction decoding processing on each of the plurality of kinds of encoded information data groups demultiplexed by the demultiplexing means; a first error correction decoding means for dividing each of the decoded information data groups yielded by the second error correction decoding means into encoded information data of an important part and decoded information data of an unimportant part on the basis of first header information included in the decoded information data group, and conducting first error correction decoding processing on the encoded information data of the important part; and a means for reproducing original information data from decoded information data of the important part yielded by the first error correction decoding means and the decoded information data of the unimportant part.
Even if the transmission channel quality is poor, such a configuration makes it possible to reproduce the encoded data of the important part accurately by conducting the error correction decoding processing. As a result, the original data can be reproduced to such a degree that the user can at least decipher it.
(32) In a multiplexing apparatus of an information data multiplex transmission system for inserting a plurality of kinds of information data into one packet and conducting multiplex transmission,
the multiplexing apparatus includes: a division means for dividing each of the plurality of kinds of information data into an important part and an unimportant part; an error correction encoding means for conducting error correction encoding on the important part resulting from the division in the division means by using an error correction code; a header generation means for generating first header information representing a boundary between encoded information data of the important part yielded by the error correction encoding means and information data of the unimportant part; a multiplexing means for inserting new information data each including the encoded information data of the important part yielded by the error correction encoding means, the header information generated by the header generation means, and the information data of the unimportant part, into predetermined positions of the packet, respectively; and a means for adding second header information representing a multiplexing state thereof to the new information data multiplexed by the multiplexing means and transmitting resulting information data.
Owing to such a configuration, it becomes possible to provide an important part of the information data with an error correction function. As compared with case where all information data are subjected to error correction coding under the same condition, therefore, the information data can be efficiently protected. against errors without lowering the transmission efficiency.
(33) In the configuration of (32), the header generation means has a function of generating an error detection code for conducting error detection of the first header information, and the multiplexing means inserts new information data each including the encoded information data of the important part yielded by the error correction encoding means, the first header information generated by the header generation means, and the information data of the unimportant part, into predetermined positions of the packet, respectively.
By doing so, an error of the first header information can be detected in the apparatus of the receiving side.
(34) In a demultiplexing apparatus of an information data multiplex transmission system for inserting a plurality of kinds of information data into one packet and conducting multiplex transmission,
the demultiplexing apparatus includes: a demultiplexing means for demultiplexing a plurality of kinds of information data groups inserted in a received packet, on the basis of second header information representing a multiplex state thereof; an error correction decoding means for dividing each of the plurality kinds of information data groups demultiplexed by the demultiplexing means into encoded information data of an important part and information data of an unimportant part on the basis of first header information included in the information data group, and conducting error correction decoding processing on the encoded information data of the important part; and a means for reproducing original information data from decoded information data of the important part yielded by the error correction decoding means and the information data of the unimportant part.
(35) In an error correction encoding apparatus provided in an information transmission apparatus,
the error correction encoding apparatus includes: a first error correction encoding means for generating a first inspection signal sequence for a first information signal sequence and a second information signal sequence requiring more intense error protection than the first information signal sequence; a transmitting interleaving means for changing element order of the second information signal sequence; a second error correction encoding means for generating a second inspection signal sequence for the second information signal sequence changed in order by the transmitting interleaving means; and a transmitting means for transmitting an encoded signal including the first and second information signal sequences and the first and second inspection signal sequences onto a transmission channel.
In such an error correction encoding apparatus, it is possible to conduct double error correction encoding on the second information signal which is included and the transmission information and which requires intense error protection.
(36) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus described in (35),
the error correction decoding apparatus includes: a first error correction decoding means for conducting error correction decoding on the first and second information signal sequences included in the received encoded signal, on the basis of the first inspection signal sequence included in the encoded signal, and outputting first and second decoded information signal sequences; a receiving interleaving means for changing element order of the second decoded information signal sequence output from the first error correction decoding means; a second error correction decoding means for conducting error correction decoding on the second decoded information signal sequence changed in order by the receiving interleaving means, on the basis of the second inspection signal sequence included in the received encoded signal, and outputting the second decoded information signal sequence further subjected to the error correction; and a receiving de-interleaving means for restoring the second decoded information signal sequence output from the second error correction decoding means, to the original element order.
(37) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus described in (35),
the error correction decoding apparatus includes: a receiving interleaving means for changing element order of the second decoded information signal sequence included in the received encoded signal; a second error correction decoding means for conducting error correction decoding on the second decoded information signal sequence changed in order by the receiving interleaving means, on the basis of the second inspection signal sequence included in the received encoded signal, and outputting the second decoded information signal sequence; a receiving de-interleaving means for restoring the second decoded information signal sequence output from the second error correction decoding means, to the original element order; and a first error correction decoding means for conducting error correction decoding on the second decoded information signal sequence output from the receiving de-interleaving means and the first information signal sequence included in the received encoded signal, on the basis of the first inspection signal sequence included in the received encoded signal, and outputting the first decoded information signal sequence and the second decoded information signal sequence further subjected to the error correction.
In the error correction decoding apparatuses described in (36) and (37), it is possible to conduct double error correction decoding on the second information signal which is included in the information signals transmitted from the transmitting side and which requires intense error protection. As a result, highly reliable information decoding can be conducted while suppressing the degradation of the transmission efficiency.
(38) In the configuration of (36) or (37), the first and second error correction decoding means has an iterative decoding function of iterating the error correction decoding processing between them at least once.
By providing such a function, further highly reliable decoding becomes possible.
(39) In the configuration of (38), the error correction decoding apparatus further includes an iteration control means for determining number of times of iteration according to at least one of a demanded error correction capability and a permitted processing delay amount, and setting the determined number of times of iteration into the first and second error correction decoding means.
By providing such a means, optimum iterative decoding processing is conducted according to the demanded error correction capability and the permitted processing delay amount.
(40) In the configuration of (35), the error correction decoding apparatus includes, besides the first and second error correction decoding means, a third error correction decoding means for iterating error correction decoding processing between the first error correction decoding means and the second error correction decoding means at least once, and outputting the first and second decoded information signal sequences thus subjected to iterative decoding; and a selection means for selecting one of the first, second, and third error correction decoding means on the basis of at least one of a transmission channel state and a property of the transmitted information signal sequences, and causing error correction decoding processing to be conducted.
(41) The error correction decoding apparatus includes, besides the first and second error correction decoding means provided in the error correction decoding apparatus of (35), a third error correction decoding means for iterating error correction decoding processing between the first error correction decoding means and the second error correction decoding means at least once, and outputting the first and second decoded information signal sequences thus subjected to iterative decoding; and a selection means for selecting one of the first, second, and third error correction decoding means on the basis of at least one of a transmission channel state and a property of the transmitted information signal sequences, and causing error correction decoding processing to be conducted.
In the error correction decoding apparatuses of (40) and (41), optimum error correction decoding means is selected according to the transmission channel state at each time and the property of the transmitted information signal, and the information signal is decoded.
(42) In an error correction encoding apparatus for conducting error correction encoding on a first information signal sequence and a second information signal sequence requiring more intense error protection than the first information signal sequence, and transmitting the encoded first information signal sequence and second information signal sequence,
the error correction encoding apparatus includes: a transmitting interleaving means for changing element order of the second information signal sequence; a first error correction encoding means for generating a first inspection signal sequence for the second information signal sequence changed in order by the transmitting interleaving means and the first information signal sequence; a second error correction encoding means for generating a second inspection signal sequence for the second information signal sequence; and a transmitting means for transmitting an encoded signal including the first and second information signal sequences and the first and second inspection signal sequences onto a transmission channel.
When inputting the second information signal sequence to the second error correction encoding means, it is input as it is, in such a configuration. When inputting the first and second information signal sequences to the first error correction encoding means, interleaving is conducted on the second information signal sequence. In the case where it is attempted to reproduce on the receiving side only the second information signal sequence, therefore, it can be advantageously reproduced by simple processing without conducting interleaving and de-interleaving.
(43) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (42),
the error correction decoding apparatus includes: a second error correction decoding means for conducting error correction decoding on the second information signal sequence included in the received encoded signal, on the basis of the second inspection signal sequence included in the encoded signal, and outputting a second decoded information signal sequence; a receiving interleaving means for changing element order of the second decoded information signal sequence output from the second error correction decoding means; a second error correction decoding means for conducting error correction decoding on the second decoded information signal sequence changed in order by the receiving interleaving means and the first information signal sequence included in the received encoded signal, on the basis of the first inspection signal sequence included in the received encoded signal, and outputting a first decoded information signal sequence and the second decoded information signal sequence further subjected to the error correction; and a receiving de-interleaving means for restoring the second decoded information signal sequence output from the second error correction decoding means, to the original element order.
In such a configuration, double error correction decoding processing is conducted on the second information signal sequence having high importance by the second and first error correction decoding means. For example, in such a state that the transmission channel quality is degraded as in a mobile communication system, therefore, the possibility that at least the second information signal sequence can be decoded correctly becomes high.
(44) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (42),
the error correction decoding apparatus includes: a second error correction decoding means for conducting error correction decoding on the second information signal sequence included in the received encoded signal, on the basis of the second inspection signal sequence included in the encoded signal, and outputting a second decoded information signal sequence; a receiving interleaving means for changing element order of the second decoded information signal sequence output from the second error correction decoding means; a second error correction decoding means for conducting error correction decoding on the second decoded information signal sequence changed in order by the receiving interleaving means and the first information signal sequence included in the received encoded signal, on the basis of the first inspection signal sequence included in the received encoded signal, and outputting a first decoded information signal sequence and the second decoded information signal sequence further subjected to the error correction; and a receiving de-interleaving means for restoring the second decoded information signal sequence output from the second error correction decoding means, to the original element order.
In such a configuration as well, double error correction decoding processing is conducted on the second information signal sequence having high importance by the second and first error correction decoding means. Even in the case where the transmission channel quality is degraded, therefore, the possibility that the second information signal sequence can be decoded correctly becomes high.
(45) In the configuration of (43) or (44), the first and second error correction decoding means has an iterative decoding function of iterating the error correction decoding processing between them at least once.
In such a configuration, decoding utilizing the iteration of the most likelihood decoding is conducted in the first and second error correction decoding means. Therefore, decoding having a further higher error correction capability can be effected. Even in the case where a transmission channel having a poor quality is used, transmission of a high quality can be effected.
(46) In the configuration of (43) or (44), the error correction decoding apparatus further includes an iteration control means for determining number of times of iteration according to at least one of a demanded error correction capability and a permitted processing delay amount, and setting the determined number of times of iteration into the first and second error correction decoding means.
Even if the demanded error correction capability or the permitted processing delay amount is altered after the receiving apparatus is put in service, an optimum number of times of iteration can always be determined by the iteration control means in such a configuration.
(47) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (42),
the error correction decoding apparatus includes: a second error correction decoding means for conducting error correction decoding on the second information signal sequences included in the received encoded signal, on the basis of the second inspection signal sequence included in the encoded signal, and outputting a second decoded information signal sequence; a second error correction decoding means for conducting error correction decoding on a signal sequence obtained by conducting interleaving on the second decoded information signal sequence output from the second error correction decoding means, and the first information signal sequence included in the received encoded signal, on the basis of the first inspection signal sequence included in the received encoded signal, thereby yielding a first decoded information signal sequence and the second decoded information signal sequence further subjected to the error correction, conducting de-interleaving on the second decoded information signal sequence, and outputting the first decoded information signal sequence and the second decoded information signal sequence thus interleaved; a third error correction decoding means for iterating error correction decoding processing between the first error correction decoding means and the second error correction decoding means at least once, and outputting the first and second decoded information signal sequences thus subjected to iterative decoding; and a selection means for causing the error correction decoding processing using only the first error correction decoding means, the error correction decoding processing using the first and second error correction decoding means, and the error correction decoding processing using the first, second, and third error correction decoding means to be selectively executed, on the basis of at least one of a transmission channel state and a property of the transmitted information signal sequences.
(48) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (42),
the error correction decoding apparatus includes: a first error correction decoding means for conducting error correction decoding on a signal sequence obtained by conducting interleaving on the second decoded information signal sequence included in the received encoded signal, and the first information signal sequence included in the received encoded signal, on the basis of the first inspection signal sequence included in the received encoded signal, and outputting first and second decoded information signal sequence; a second error correction decoding means for conducting de-interleaving the second decoded information signal sequence output from the first error correction decoding means, then conducting error correction decoding on the second decoded information signal sequence thus de-interleaved, on the basis of the second inspection signal sequence included in the received encoded signal, and outputting the second decoded information signal sequence further subjected to the error correction; a third error correction decoding means for iterating error correction decoding processing between the first error correction decoding means and the second error correction decoding means at least once, and outputting the first and second decoded information signal sequences thus subjected to iterative decoding; and a selection means for causing the error correction decoding processing using only the first error correction decoding means, the error correction decoding processing using the first and second error correction decoding means, and the error correction decoding processing using the first, second, and third error correction decoding means to be selectively executed, on the basis of at least one of a transmission channel state and a property of the transmitted information signal sequences.
In the configurations of (47) and (48), the error correction decoding processing using only the first error correction decoding means, the error correction decoding processing using the first and second error correction decoding means, and the error correction decoding processing using the first, second, and third error correction decoding means are selectively conducted on the basis of the transmission channel state or the property of the transmitted information signal sequences. According to the transmission channel state at each time and the property of the transmitted information signal sequences, therefore, optimum error correction decoding processing is always effected. As a result, efficient error correction decoding having a high error correction capability can be conducted.
(49) In the configuration of (35) or (42), unimportant information requiring a predetermined transmission quality is assigned to the first information signal sequence, and important information requiring a higher transmission quality than the first information signal sequence is assigned to the second information signal sequence.
In the case where, for example, image data are transmitted, important information such as various kinds of control information, movement prediction information, and low frequency components of the discrete cosine transform (DCT) is assigned to the second information signal sequence, and unimportant information such as high frequency components of the DCT is assigned to the first information signal sequence, in such a configuration. Even under such a condition that the transmission quality is poor, at least various kinds of information which is important in forming images can be reproduced correctly. As a result, images which are sufficiently decipherable can be reconstructed. Furthermore, as compared with the case where all kinds of information are transmitted as the second information signal sequence, a high transmission efficiency can be ensured.
(50) In the configuration of (35) or (42), information transmitted by using a first transmission scheme having a predetermined intensity against transmission errors is assigned to the first information signal sequence, and information transmitted by using a second transmission scheme having an intensity against transmission errors lower than that of the first transmission scheme is assigned to the second information signal sequence.
An information signal transmitted by using a: modulation scheme having a short distance between signal points, such as 16 QAM scheme or 64 QAM scheme, is susceptible to errors. In such a configuration, therefore, this information signal is transmitted as the second information signal sequence. On the other hand, since an information signal transmitted by using a modulation scheme having a long distance between signal points, such as QPSK scheme, is not susceptible to errors, this information signal can be transmitted as the first information signal sequence. By doing so, it is possible to provide all information signals with a uniform error correction capability and transmit them.
(51) The error correction encoding apparatus includes: a first error correction encoding means for generating a first two-dimensional inspection block having (Nxe2x88x92K)xc3x97L elements in a horizontal direction of a first two-dimensional information block having Kxc3x97L elements, in accordance with a first error correction encoding rule; a second error correction encoding means for generating a second two-dimensional inspection block having K2xc3x97(Mxe2x88x92L) elements in a vertical direction of a second two-dimensional information block having K2xc3x97L elements (where K greater than K2) requiring especially intense error protection included in the first two-dimensional information block, in accordance with a second error correction encoding rule; and a transmitting means for transmitting an encoded signal including the first two-dimensional information block and the first and second inspection blocks onto a transmission channel.
In such a configuration, information can be handled by taking a block as the unit. Therefore, error correction encoding, decoding and transmission suitable for such a system that an information signal sequence is transmitted by taking a byte or an octet as the unit. In addition, error correction is conducted for the whole of the first information block in the horizontal direction. For the second information block having especially high importance in the first information block, error correction is conducted for its vertical direction. As compared with the case where error correction of the horizontal direction and the vertical direction is conducted for the whole of the information block, efficient error correction decoding processing can be conducted by only adding a small number of inspection blocks.
(52) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (51),
the error correction decoding apparatus includes: a first error correction decoding means for conducting error correction decoding for the horizontal direction of the first two-dimensional information block included in the received encoded signal, on the basis of the first two-dimensional inspection block included in the encoded signal, and outputting a first decoded two-dimensional information block; and a second error correction decoding means for conducting error correction decoding for the vertical direction of an information block included in the first decoded two-dimensional information block output the first error correction decoding means, corresponding to the second two-dimensional information block, on the basis of the second two-dimensional inspection block included in the received encoded signal, and outputting a second decoded two-dimensional information block.
In such a configuration, double error correction decoding processing is conducted on the second two-dimensional information block having high importance by the second and first error correction decoding means. Even in such a state that the transmission channel quality is degraded as in a mobile communication system, therefore, the possibility that at least the second two-dimensional information block can be decoded correctly becomes high.
(53) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (51),
the error correction decoding apparatus includes: a second error correction decoding means for conducting error correction decoding for the vertical direction of an information block included in the received encoded signal, corresponding to the second two-dimensional information block, on the basis of the second two-dimensional inspection block included in the received encoded signal, and outputting a second decoded two-dimensional information block; and a first error correction decoding means for conducting error correction decoding for the horizontal direction of the second decoded two-dimensional information block output from the second error correction decoding means and the first two-dimensional information block included in the received encoded signal, on the basis of the first two-dimensional inspection block included in the encoded signal, and outputting a first decoded two-dimensional information block, and the second decoded two-dimensional information block further subjected to the error correction.
In such a configuration as well, double error correction decoding processing is conducted on the second two-dimensional information block having high importance by the second and first error correction decoding means. Even in such a state that the transmission channel quality is degraded as in a mobile communication system, therefore, the possibility that the second two-dimensional information block can be decoded correctly becomes high.
(54) In the configuration of (52) or (53), the first and second error correction decoding means has an iterative decoding function of iterating the error correction decoding processing between them at least once.
In such a configuration, decoding untilizing the iteration of the most likelihood is conducted in the first and second error correction decoding means. Therefore, decoding having a further higher error correction capability can be conducted. Even in the case where a transmission channel having a poor transmission channel quality is used, therefore, high quality transmission can be effected.
(55) In the configuration of (54), the error correction decoding apparatus further includes an iteration control means for determining number of times of iteration according to at least one of a demanded error correction capability and a permitted processing delay amount, and setting the determined number of times of iteration into the first and second error correction decoding means.
Even if the demanded error correction capability or the permitted processing delay amount is altered after the receiving apparatus is put in service, an optimum number of times of iteration can always be determined by the iteration control means in such a configuration.
(56) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (51),
the error correction decoding apparatus includes: a first error correction decoding means for conducting error correction decoding for the horizontal direction of the first two-dimensional information block included in the received encoded signal, on the basis of the first two-dimensional inspection block included in the encoded signal, and outputting a first decoded two-dimensional information block; a second error correction decoding means for conducting error correction decoding for the vertical direction of an information block included in the first decoded two-dimensional information block output the first error correction decoding means, corresponding to the second two-dimensional information block, on the basis of the second two-dimensional inspection block included in the received encoded signal, and outputting a second decoded two-dimensional information block; a third error correction decoding means for iterating error correction decoding processing between the first error correction decoding means and the second error correction decoding means at least once, and outputting the first and second decoded two-dimensional information blocks thus subjected to iterative decoding; and a selection means for causing the error correction decoding processing using only the first error correction decoding means, the error correction decoding processing respectively using the first and second error correction decoding means, and the error correction decoding processing respectively using the first, second, and third error correction decoding means to be selectively executed, on the basis of at least one of a transmission channel state and a property of the transmitted information signal.
(57) In an error correction decoding apparatus for receiving and decoding the encoded signal transmitted from the error correction encoding apparatus of (51),
the error correction decoding apparatus includes: a second error correction decoding means for conducting error correction decoding for the vertical direction of an information block included in the received encoded signal, corresponding to the second two-dimensional information block, on the basis of the second two-dimensional inspection block included in the received encoded signal, and outputting a second decoded two-dimensional information block; and a first error correction decoding means for conducting error correction decoding for the horizontal direction of the second decoded two-dimensional information block output from the second error correction decoding means and the first two-dimensional information block included in the received encoded signal, on the basis of the first two-dimensional inspection block included in the encoded signal, and outputting a first decoded two-dimensional information block, and the second decoded two-dimensional information block further subjected to the error correction; a third error correction decoding means for iterating error correction decoding processing between the first error correction decoding means and the second error correction decoding means at least once, and outputting the first and second decoded two-dimensional information blocks thus subjected to iterative decoding; and a selection means for causing the error correction decoding processing using only the first error correction decoding means, the error correction decoding processing respectively using the first and second error correction decoding means, and the error correction decoding processing respectively using the first, second, and third error correction decoding means to be selectively executed, on the basis of at least one of a transmission channel state and a property of the transmitted information signal.
In the configurations of (56) and (57), the error correction decoding processing using only the first error correction decoding means, the error correction decoding processing using the first and second error correction decoding means, and the error correction decoding processing using the first, second, and third error correction decoding means are selectively conducted on the basis of the transmission channel state or the property of the transmitted information signal sequences. According to the transmission channel state at each time and the property of the transmitted two-dimensional information block, therefore, optimum error correction decoding processing is always effected. As a result, efficient error correction decoding having a high error correction capability can be conducted.
(58) In the configuration of (51), unimportant information requiring a predetermined first transmission quality is assigned to the first two-dimensional information block except the second two-dimensional information block, and important information requiring a higher transmission quality than the first transmission quality is assigned to the second two-dimensional information block.
In the case where, for example, image data are transmitted as a two-dimensional block, important information such as various kinds of control information, movement prediction information, and low frequency components of the discrete cosine transform (DCT) is assigned to the second two-dimensional information block, and unimportant information such as high frequency components of the DCT is assigned to the first two-dimensional information block, in such a configuration. Even under such a condition that the transmission quality is poor, at least various kinds of two-dimensional block which is important in forming images can be reproduced correctly. As a result, images which are sufficiently decipherable can be reconstructed. Furthermore, as compared with the case where all kinds of information are transmitted as the second two-dimensional information block, a high transmission efficiency can be ensured.
(59) In the configuration of (51), information transmitted by using a first transmission scheme having a predetermined intensity against transmission errors is assigned to the first two-dimensional information block except the second two-dimensional information block, and information transmitted by using a second transmission scheme having an intensity against transmission errors lower than that of the first transmission scheme is assigned to the second two-dimensional information block.
In such a configuration, transmitted information is assigned to the first or second two-dimensional information block according to the error resistance performance of the modulation scheme in use. As a result, it is possible to provide every transmitted information with a uniform error correction capability in transmission.
(60) In the configuration of (38), (45) or (54), the error correction decoding apparatus further includes, on an input side of the first and second error correction decoding means, a normalization means for normalizing a signal level of each of signal sequences or signal blocks to be input to the first and second error correction decoding means, on the basis of a level of the received encoded signal.
Owing to such a configuration, it is possible to occurrence of such inconvenience that the Euclidean distance becomes large despite the fact that the reliability information is raised by iterative decoding. As a result, the decoding precision can be raised.